As a conventional method of forming a Ga2O3 single crystal, a method is known in which a Group IV element such as Si or Sn is added while growing a Ga2O3 single crystal to impart conductivity to the Ga2O3 single crystal (see, e.g., PTL 1).
Meanwhile, as another conventional method of forming a Ga2O3 single crystal, a method is known in which a β-Ga2O3 crystal is heteroepitaxially grown on a sapphire substrate while adding an impurity such as Sn to form a β-Ga2O3 crystal film having conductivity (see, e.g., PTL 2).
A method in which an impurity ion is introduced into a SiC crystal by ion implantation process is also known (see, e.g., PTL 3).